The effects of hyperthermia, microwave and ultrasound treatment of tumor cells on different parameters of the immune response to tumor antigens is being evaluated using a syngeneic hamster tumor system. Research in this area could lead to the development of techniques which render tumor cells more immunogenic and/or antigenic, perhaps resulting in enhancement of tumor rejection mechanisms. The work includes primarily in vitro experiments which will result in a quantitative description of changes in sensitivity of tumor cells to immune lysis following treatment, and in vivo tests to determine the immunological effects of treatment of growing tumors by hyperthermia induced by ultrasound or microwave radiation.